Probably because you already have them in the most recent hash key file you received; it's only newer disks that you would need to have the latest one.

Check your DNS; if you're not using Google as one of your DNS servers, you may be getting bogus results for the domain that MakeMKV uses, due to "content filtering". And some software will block access to the domain. But, until you can connect and download the latest HK file, you won't be able to decrypt the disk.